This invention relates generally to improvements in fluid dispersing apparatus and methods of applying fluids to precise locations of hollow objects utilizing centrifugal force. One application of the invention is the application of liquid to the internal threads of a fastener nut.
Various coatings of fluid materials are applied to the internal surfaces of hollow objects such as nut type fasteners by a variety of coating systems. For example, "Teflon" (trademark of E. I. DuPont de Nemours & Co.) sealant is applied to the threads of nuts in order to provide an improved seal. The presence of the Teflon compound interferes with subsequent plating or surface coating if the Teflon is leaked onto the exterior surfaces.
For example, Teflon coated fasteners are used extensively in the automotive industry where steel parts are commonly immersed and coated with an electrodeposited rust inhibitor. A Teflon coating prevents the rust inhibitor solution from adhering to selected surfaces where the rust inhibitor layer may interfere with subsequent assembly requirements. For example, it is often desirable to maintain internal threads of fasteners free of the rust inhibitor to provide more reliable fit-up and assembly. Fasteners which have a Teflon coating on their internal threads can be immersed into a rust inhibitor bath along with an entire automotive assembly while maintaining selected surfaces where the rust inhibitor will not adhere. This is accomplished without the use of previous labor intensive, and often ineffective rubber plugs. In subsequent assembly, the Teflon coating readily yields to the insertion of a mating external thread.
The process of the present invention teaches coating on a repetitive part basis to pre-selected surfaces, such as the threaded cavities of nuts, and avoids contamination of adjacent and exterior surfaces. The apparatus for practicing the described process uses substantially all of the material to coat the nut, thereby eliminating waste.
U.S. Pat. No. 4,652,468 to Gould, et al. discloses a process for high pressure impact coating of portions of work pieces such as threaded openings and fasteners and avoidance of contaminating portions of the work piece with the coating material. The process requires masking of the surfaces of the nut in order to restrict material from contaminating the outer surfaces of the nut. Additionally, the machine requires a choked area for sucking the waste material from the fastener. Illustrated preferred embodiments of the present invention provide a precise amount of material to selected surfaces of the nut and eliminates the need to suck waste material from the nut.
U.S. Pat. No. 4,528,938 to Nevel discloses a rotary work piece treating apparatus for depositing coating or adhesive materials within threaded fastener nuts. The device includes a continuously rotating turntable assembly having a plurality of work station cylinders attached thereto. A probe attached to the plunger is caused to enter within the internal bore of the nuts and release flowable material within the nut. The flow of such material is controlled by a valve stem protruding from the probe which is depressed against the stop surface when the probe is inserted within the nuts. Certain preferred embodiments of the present invention utilize straight line feeding and eliminates the valve stem control for the material.
Other prior art such as U.S. Pat. Nos. 4,060,868 to Axvig and 3,896,760 to R. J. Duffy disclose systems and methods for coating the interior surfaces of pipes using a low pressure application of dry resin material to the interior of heated pipe sections. These disclosures do not address the problem of controlling the flow of liquid material to a selected surface with precise isolation from portions not to be coated with the liquid material.
Accordingly, it is an object of the present invention to provide an improved method and apparatus for applying a precise liquid coating to predetermined selected surfaces of hollow objects utilizing centrifugal force to disperse a metered quantity of fluid material.
It is another object of the present invention to rapidly apply fluid coatings to objects utilizing centrifugal force from the rotation of a probe inserted into the hollow cavity of an object.
It is another object of the invention to provide a process and apparatus which will eliminate waste material, thereby reducing material costs and ultimately disposal costs for the waste material.
It is another object of the invention to provide an apparatus and process for coating objects which will reduce production and maintenance labor.
It is another object of the invention to provide an apparatus and process which will eliminate utility costs, particularly the volume of air needed in the coating process.
It is another object of the invention to provide a process and apparatus which eliminates the need for sealing and/or masking of the object to be coated.
It is another object of the invention to provide a process and apparatus which can control the coating process by calculating the metered pumping rate, and the up and down cycle of the probe.
It is another object of the invention to provide an apparatus and system which applies a uniform coating to a precise portion of the object to be coated.
It is another object of the invention to provide a system which recirculates the coating material thereby restricting settlement problems in the material.
It is another object of the invention to provide a machine which reduces noise, spillage, and other problems in the work place.
It is another object of the invention to eliminate high pressure delivery lines for coating objects.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments in the appended claims, taken in conjunction with the accompanying drawings.
The above objects are accomplished with the apparatus and process for coating hollow objects with fluid materials according to this invention. The apparatus and process described herein utilizes centrifugal force to disperse fluid from a probe. The apparatus meters a precise amount of fluid thereby eliminating waste of excess material and the need to mask the article. Preferred embodiments of the present invention incorporate a conveying device for moving a succession of workpieces, for example, internally threaded articles, into position for application of fluid. In certain preferred embodiments, a rotating hollow probe is then moved from under the object into a coating position. Preferably, the probe is simultaneously moved upward through the workpiece coating the object as the material is pumped from a holding chamber through the metering pump, thereby metering the volume of fluid, and dispersed by the centrifugal force from the rotary motion of the probe. In certain preferred embodiments, when the selected area has been coated, the pump is reversed to pull the material away from the opening in the probe and the probe is then withdrawn from the object. In preferred embodiments, the probe dispenses a second coating during the removal from the object. The object is then preferably moved into a drying chamber where the excess vapors are drawn off from the object. The process minimizes any waste material thus improving the environmental aspects of the work place.